Page 7 - English Class X_cbse new (FINAL).cdr

Q1 (i) Obtain the expression for the torque τ experienced by an electric Q8 Two small identical electrical dipoles AB and CD, each of dipole moment
dipole of dipole moment P in a uniform electric field, E. ‘p’ are kept at an angle of 120° as shown in the figure. What is the resultant

(ii) What will happen if the field were not uniform? dipole moment of this combination? If this system is subjected to electric field

[3] Delhi Set-2 [2017] ( )E directed along + X direction, what will be the magnitude and direction of

the torque acting on this?

Y

Q2 (i) Derive the expression for electric field at a point on the equatorial line D A +q
of an electric dipole. –q

(ii) Depict the orientation of the dipole in (i) stable, (ii) unstable equilibrium 120° X
in a uniform electric field. X'

[3] Delhi Set-2 [2017]

Q3 A charge is distributed uniformly over a ring of radius ‘a’. Obtain an expres- +q [3] Delhi Set-1 [2011]
sion for the electric field intensity E at a point on the axis of the ring. Hence
show that for points at large distances from the ring, behaves like a point B –q C
charge. Y'
[3] Delhi Set-3 [2016]
Q9 In which orientation, a dipole placed in a uniform electric field is in (i) stable,
Q4 Why do the electrostatic field lines do not form closed loop? (ii) unstable equilibrium?
[1] Delhi Set-1, 2 [2015, 2014]
[1] Delhi Set-1 [2010]

Q5 Why do the electric field lines never cross each other? Q10 What is the work done in moving a test charge q through a distance of 1 cm
along the equatorial axis of an electric dipole?

[1] OD Set-2 [2009]

[1] Delhi Set-3 [2014]

Q6 An electric dipole is held in a uniform electric field. Q11 A positive point charge (+q) is kept in the vicinity of an uncharged conduct-
(i) Show that the net force acting on it is zero. ing plate. Sketch electric field lines originating from the point on to the sur-
(ii) the dipole is aligned parallel to the field. Find the work done in rotating face of the plate. Derive the expression for the electric field at the surface of
a charged conductor.
it through the angle of 180°.
[2] OD Set-3 [2012] [3] OD Set-1 [2009]

Q7 An electric dipole is held in a uniform electric field. Q12 A n infinite number of charges, each of coulomb, are placed along x–axis at
Show that the net force acting on it is zero. The dipole is aligned parallel to x = 1m, 3m, 9m and so on. Calculate the electric field at the point x = 0 due
to these charges if all the charges are of the same sign.
the field. Find the work done in rotating it through the angle of 180º. [2] Delhi Set-1 [2009]
[2] OD Set-1 [2012]
5

Physics Booklet_Unit 1_.indd 5 8/17/2018 8:35:20 AM